HU226900B1 - Polymerisation in aqueous suspension of vinyl chloride - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to the preparation of polymers and copolymers based on vinyl chloride by polymerizing vinyl chloride, alone or in combination with another vinyl derivative monomer, in aqueous suspension, using a nitroxide-type stable radical as a polymerization inhibitor.

By aqueous suspension polymerization is meant a polymerization carried out in the presence of at least one oil-soluble initiator, wherein the monomer component (alone with vinyl chloride or other vinyl derivative monomer) is mechanically dispersed in an aqueous medium containing at least one suspending agent.

The proportion of vinyl chloride in the monomer component is at least 50% by weight, preferably greater than 80% by weight. Vinyl derivative monomers that can be copolymerized with vinyl chloride in aqueous suspension are well known, and include, but are not limited to, vinyl esters such as vinyl acetate, vinylidene halides such as vinylidene chloride, butyl acrylate and methacrylic esters such as methyl methacrylate.

Commonly used suspending agents for slurry polymerization are known protective colloids, such as water-soluble polymers such as polyvinyl alcohol, polyethylene oxides, water-soluble cellulose derivatives such as methyl cellulose, polyvinylpyrrolidone. ), gelatin and vinyl acetate / maleic anhydride copolymers. The suspending agents may be used alone or in admixture, generally in an amount of 0.01 to 0.5 parts by weight, preferably 0.04 to 0.2 parts by weight, based on 100 parts by weight of the monomer component.

Usually, a pH buffering system for the aqueous medium is used. This system, for example citric acid at acidic pH and sodium bicarbonate at alkaline pH, is used in an amount of 0.01 to 0.2 parts by weight, preferably 0.02 to 0.1 parts by weight, based on 100 parts by weight of the monomer component.

The commonly used liposoluble initiator system consists of one or more compounds that generate free radicals, thereby initiating polymerization of the monomer component. These radicals are generally derived from the thermal decomposition of diacyl peroxides, dialkyl peroxydicarbonates or peroxy tertiary alkanoates. In industry, the amount of initiator added to the reaction mixture is customarily expressed as the total amount of active oxygen that can be liberated by the initiator system. Generally, the total amount of active oxygen used is between 0.0005 and 0.01 parts by weight, preferably 0.0015 to 0.005 parts by weight, per 100 parts by weight of the monomer component. When a mixture of initiators having a different half-life at a given temperature is used, the ratio may range from 1 to 99% by weight, preferably from 10 to 90% by weight. At the same temperature, the more initiators are added to the reaction mixture, the faster the reaction will be. At the same polymerization time, the higher the polymerization temperature, the less initiator remains in the reaction mixture.

In the case of a polymerization process in aqueous suspension which is batch-scale on an industrial scale, it is generally desirable to stop the polymerization after reaching a predetermined conversion rate in order to obtain a stable and uniform polymer. Sometimes it may be necessary to stop or slow the reaction in the final stage of the polymerization, i.e., when the conversion has reached more than 60% by weight, to avoid heat generation at the end of the reaction which is difficult to control with a simple double wall heat exchanger (or condenser). it may be possible to stop the polymerization immediately if the polymerization suddenly runs off. To this end, so-called polymerization inhibitors are used.

The most commonly used stopping agents ("short-stoppers" or "killers") for the polymerization of vinyl chloride in aqueous suspension are: ATSC (acetone thiosemicarbazone), bisphenol A (4,4'-isopropylidene diphenol), butyl hydroxy anisole (BHA) and Irganox® 245 (i.e. 2,4-dimethyl-6-sec-hexadecylphenol) alone or with Irganox® 1076 [i.e. octadecyl-3- (3,5-di-tert-butyl-4) -hydroxyphenyl)] - propionate]. Irganox® 1141 (hereinafter referred to as IGX 1141) is a commercial blend consisting of 80 parts by weight of Irganox® 245 and 20 parts by weight of Irganox® 1076. However, these agents are not fully satisfactory and research is ongoing into replacing them with compounds that are easier to apply (have better solubility in aqueous media) and at least as effective.

It has now been found that a system comprising an initiator combination containing a compound selected from dialkyl peroxydicarbonates, peroxy tertiary alkanoates and diacyl peroxides, and containing at least one polymerization stopping agent selected from the group consisting of stable radicals of the nitroxide type, is not only effective. polymerization, but at the same time it is possible to obtain a PVC resin or copolymer from which materials of excellent whiteness can be produced. Furthermore, compared to conventional polymerization stop agents, the nitroxide may be selected to have the advantage that it can be diluted immediately with water at the concentrations used without the addition of a stabilizer or solvent.

The present invention relates to a process for the polymerization of vinyl chloride, either alone or in a mixture with less than 50% by weight of other vinyl monomers, in an aqueous suspension, characterized in that the polymerization initiator system comprises at least one of dialkyl peroxydicarbonates, a compound selected from the group consisting of tertiary alkanoates and diacyl peroxides, and at least one polymerization inhibitor selected from the group consisting of nitroxide-type stable radicals.

In general, the polymerization of vinyl chloride or a vinyl chloride-based monomer component in an aqueous suspension is carried out at a temperature between 45 ° C and 80 ° C, preferably

It is carried out at temperatures between 900 ° C and 70 ° C, which greatly facilitates the use of initiators belonging to the dialkyl peroxydicarbonate family.

In dialkyl peroxydicarbonates, the alkyl group may have from 2 to 16 carbon atoms and may be straight, branched or cyclic. Examples of such dialkyl peroxydicarbonates include diethyl, diisopropyl, di-n-propyl, dibutyl, dicetyl, dimyristyl, di (4-tert-butylcyclohexyl), or di (2). ethyl hexyl) peroxydicarbonate. Preferred are peroxydicarbonates in which all alkyl groups contain from 6 to 16 carbon atoms, with di (2-ethylhexyl) dicarbonate being particularly preferred.

The dialyl peroxydicarbonates used in the present invention belong to the family of fast initiators. They generally have a half-life of about one hour at temperatures of about 56-67 ° C, so they can be used for vinyl chloride at polymerization temperatures of 50 to 70 ° C.

However, when the chosen polymerization temperature is not so high (between 50 and 57 ° C), it may be useful to use a combination of initiators having different half-lives at the selected temperature, such as a dialkyl peroxydicarbonate and a very fast peroxy tertiary alkanoate. or a combination of initiators belonging to the family of peroxy-tertiary alkanoates, comprising a fast initiator and a very fast initiator.

Very fast peroxy-tertiary alkanoates generally have a half-life of about 1 hour at temperatures of about 53-61 ° C. Examples of very fast initiators in the family of peroxy-tertiary alkanoates include 1,1-dimethyl-3-hydroxybutyl-peroxineodecanoate, cumyl-peroxy-neodecanoate, 1,1,3,3-tetramethyl-butyl. peroxy neodecanoate; and 1,3-di (2-neodecanoyl peroxyisopropyl) benzene.

When the polymerization temperature selected is slightly higher (between 56 and 63 ° C), it may be useful to use a combination of initiators that have different half-lives at a given temperature, such as a dialkyl peroxydicarbonate and a fast peroxy tertiary alkanoate family. combination of initiator or rapid peroxy-tertiary alkanoates.

Fast peroxy-tertiary alkanoates generally have a half-life of 1 hour at a temperature of 61 to 71 ° C, and can therefore be used at 50 to 70 ° C vinyl chloride polymerization temperatures. Examples of fast peroxy tertiary alkanoates include tert-butyl peroxy neodecanoate and tert-amyl peroxy neodecanoate.

At relatively high polymerization temperatures (between 62 and 70 ° C), it may be useful to use a combination of initiators having different half-lives at that temperature, such as a dialkyl peroxydicarbonate or a fast peroxy tertiary alkanoate and a. rather a slow initiator of the diacyl peroxide family such as dilauroyl peroxide or peroxy tertiary alkanoates such as tert-butyl peroxy pivalate.

According to the invention, the polymerization stop agent ("short-stopper" or "killer") is preferably a stable radical of the nitroxide type of formula I wherein Y ¹ -Y ⁶ , which may be the same or different, is hydrogen, C 1-10 straight or branched chain alkyl, C3-C20 cycloalkyl, halogen, cyano, phenyl, C1-C4 hydroxyalkyl, dialkoxyphosphonyl, diphenoxyphosphonyl, alkoxycarbonyl, alkoxycarbonyl; an alkyl group or two or more of Y ¹ -Y ⁶ , taken together with the carbon atom to which they are attached, may form ring structures which may contain one or more of the following rings: HO-, CH ₃ C (O) -, CH ₃ O-, H ₂ N-CH ₃ C (O) NH (CH ₃ ) ₂ N-, R ¹ C (O) O-, wherein R ¹ is a C 1-20 hydrocarbon group; or they may contain one or more heteroatoms, either ring or non-ring, such as oxygen or nitrogen.

Exemplary nitroxides of the formula I for use in the present invention include:

- 2,2,5,5-tetramethyl-1-pyrrolidinyloxy (marketed as PROXYL);

- 3-carboxy-2,2,5,5-tetramethylpyrrolidinyloxy (called 3-carbonic PROXYL);

- 2,2,6,6-tetramethyl-1-piperidinyloxy (called TEMPO);

- 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (called 4-hydroxy-TEMPO);

4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy (referred to as 4-methoxy-TEMPO);

- 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (called 4-oxo-TEMPO);

4-amino-2,2,6,6-tetramethyl-1-piperidinyloxy (referred to as 4-amino-TEMPO);

- 4-acetamido-2,2,6,6-tetramethyl-1-piperidinyloxy (referred to as 4-acetamido-TEMPO);

- N-tert-butyl-1-phenyl-2-methylpropyl nitroxide,

- N- (2-hydroxymethylpropyl) -1-phenyl-2-methylpropylnitroxide),

- N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide,

- N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,

- N-tert-butyl-1-di (2,2,2-trifluoroethyl) phosphono-2,2-dimethylpropyl nitroxide,

- N-tert-butyl [(1-diethylphosphono) -2-methylpropyl] nitroxide,

- N- (1-methylethyl) -1-cyclohexyl-1- (diethylphosphono) nitroxide,

- N - (1-phenylbenzyl) - [(1-diethylphosphono) -1-methylethyl] nitroxide;

- N-Phenyl-1-diethylphosphono-2,2-dimethyl-1-propyl Initroxide,

- N-phenyl-1-diethylphosphono-1-methylethyl nitroxide,

- N- (1-phenyl-2-methylpropyl) -1-diethylphosphonomethyl-ethyl-nitroxide,

bis-1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate, which is disclosed in CIBA SPEC. Chem. is marketed as "CXA 5415".

HU 226 900 Β1

These nitroxides may be used alone or in the form of preparations.

A composition according to the invention is an aqueous, organic or aqueous-organic composition comprising at least one nitroxide and optionally containing an organic and / or inorganic additive (e.g., NaCl, NaOH, KOH). Examples of organic solvents that may be used in organic or aqueous organic formulations include alcohols such as methanol or ethanol.

Preferred according to the invention are 4-hydroxy-TEMPO and N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

Preferably, 4-hydroxy-TEMPO is used in a formulation having a concentration of 0.01 to 90% by weight of 4-hydroxy-TEMPO.

The process of the present invention can be carried out in a manner known per se, for example by dissolving a protective colloid in an aqueous medium or one of the monomer components, then dispersing or dissolving the fat soluble polymerization initiator in the aqueous medium and dissolving the pH of the aqueous medium. Traces of oxygen are removed so that the residual oxygen content in water is between 0.0005 and 0.05 parts by weight, preferably between 0.001 and 0.02 parts by weight, based on 100 parts by weight of water. The monomer component is then added to the reactor and the reaction mixture is stirred and heated to a temperature of 45 to 80 ° C, preferably 50 to 70 ° C.

It is not necessary to maintain a constant pressure and temperature of the reaction mixture during the polymerization. Increasing the temperature in a programmed manner, either at the beginning of the polymerization or at the end of the polymerization cycle, can accelerate the decomposition rate of the initiators and the rate of polymerization. If this temperature and pressure are kept constant, the molecular weight of the polymer chains will have a polydispersity of between 1.8 and 2.5. When the polymerization is carried out at a programmed temperature increase throughout the polymerization, a polydispersity of between 1.8 and 3.5 is obtained.

At the end of the polymerization, the monomer content of the liquid monomer phase is reduced, resulting in a change in the liquid / vapor balance of the monomer and a drop in pressure. As a result of the pressure drop, the monomer conversion is 65-75%.

As a "short-stopper", the nitroxide used in the present invention is added at a conversion of 60 to 90% by weight, preferably 70 to 80%, i.e. when the pressure drop has already occurred. The amount of nitroxide to be used for 100 parts by weight of the monomer component is from 0.0001 to 0.1 parts by weight, preferably from 0.00015 to 0.01 parts by weight.

The nitroxide used in the present invention may be used in combination with other polymerization inhibitors such as dialkylhydroxylamines such as diethylhydroxylamine (DEHA).

After the polymerization is complete, the resulting polymer is separated from the aqueous medium, then centrifuged and dried. It is generally in the form of granular particles having a particle size of 80 to 250 µm.

The invention is illustrated by the following non-limiting Examples. Unless otherwise indicated, the parts and percentages given in the examples are parts by weight and / or percent, respectively.

EXAMPLE 1 14 kg of deionized water, 2.52 g of citric acid, 3.73 g of polyvinyl alcohol were added to a 1 liter (control) liter three-way Impeller stirrer and heated jacketed reactor with stirring at 250 rpm. having a degree of hydrolysis of 78 mol%, 3.73 g of polyvinyl alcohol having a degree of hydrolysis of 72 mol%, 8.08 g of an aqueous solution of polyvinyl alcohol (containing 39% active ingredient) having a degree of hydrolysis of 55 mol% and 13.63 g di (2-ethylhexyl) peroxydicarbonate emulsion with 40% active ingredient (Luperox® 223 EN40). The active oxygen content is then 28 ppm relative to the weight of the vinyl chloride monomer (hereinafter referred to as "VKM") to be added. The reactor was then sealed and placed under partial vacuum (6.66 absolute kPa) and maintained for 15 minutes. The agitation is then increased to 330 rpm and 9 kg of VKM is added.

Cold water is circulated in the reactor jacket to control the heating so that the polymerization temperature reaches 56.5 ° C within 30 minutes. The moment when the polymerization medium reaches a temperature of 56.5 ° C, considered to be the beginning of the polymerization (time = t _0), it is found at that moment pressure (P _o) will be the reference base.

After minutes of polymerization (i.e., at _p + 3O minutes time) at a flow rate continuously 1.2 kg / hr, the reactor was charged with 4 kg of water in order to improve the coil formation of the heat exchange surfaces of the reactor constantly keeping and to reduce the viscosity of the aqueous suspension of After 60% conversion of VKM to PVC. This transformation is calculated using the heat balance at the edges of the reactor.

The effect of reducing the gas phase concentration of the VKM in the reactor is to reduce the pressure between 65 and 70% conversion. As the pressure is reduced to 1 bar with respect to P _0, the polymerization is stopped, so that the medium was rapidly cooled by injecting cold water in the reactor jacket.

The residual concentration of di (2-ethylhexyl) peroxydicarbonate is about 90 ppm relative to the initial weight of the monomer.

The residual VKM is then removed from the reaction medium by conventional means, i.e., atmospheric pressure restoration (degassing) and then the VKM traces are removed by stripping at 50 DEG C. under vacuum (13.33 kPa).

The resulting PVC resin (K value = 67) was centrifuged, dried in a fluid bed with a stream of dry air heated to 50 ° C for 6 hours, and sieved through a 500 µm screen.

HU 226 900 Β1

The color index of the resin on a pressed plate or WIPP-η (White Index Pressed Plate) is determined as follows:

In a 600 ml BRABENDER mixer, 150 g of resin is mixed with 12 g of a solution of 1 part of dioctyl phthalate in 17 parts of MOK (tin-containing heat-stabilizing solution in liquid form, manufactured by CIBA) for 5 minutes at 50 rpm and 96 ° C. markets). The mixture is removed from the mixer and within a maximum of 15 minutes, a WEBER press is used to press 20 g of the mixture for 2 minutes at 184 DEG C. at 300 bar, 70 mm diameter and 3 mm thick, between two 0.05 mm thick aluminum foils. The resulting plate is then cooled in water for 45 seconds, and after 30 to 90 minutes of compression, the discoloration is measured in a HUNTERLAB D 25 M DP 9000 and expressed as follows according to ASTM E 313 WlPP:

WIPPEL = - (L-5,71b)

100 in formula a the values of L and b are given by the device.

2-4. examples

The procedure of Example 1, except that, as the pressure drop had reached 0.3 bar (that is, the pressure P ₀ = -0.3 bar), and 2 minutes the reaction mixture was injected into a 0.04% - aqueous solution of 4-hydroxyTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy, hereinafter abbreviated as OH-TEMPO) at 1.5, 3 and 6 ppm relative to the initial mass of the VKM mass of OH-TEMPO and the reaction mixture was heated at 56.5 ° C for 15 minutes and then cooled. Then degassing, stripping, centrifugation, drying and sieving were performed in the same manner as in Example 1 and the resulting PVC resins were evaluated by the same assay as WIPP.

Example 5

Same as for Example 1 above, with the exception that as the pressure drop reaches 0.3 bar (that is, the pressure P ₀ = -0.3 bar), the reaction mixture 5.35% methanol SG1- (N A solution of tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide) was added at 115 ppm relative to the initial weight of the VKM, and the reaction mixture was heated at 56.5 ° C for 15 minutes and then cooled. Degassing, stripping, centrifugation, drying and sieving were performed in the same manner as in Example 1.

Example 6

Proceed as in Example 1, except that as soon as the pressure drop reaches 0.3 bar (i.e., pressure = P ₀ -0.3 bar), OH-TEMPO and DEHA is injected into the reaction mixture to the initial mass of the VKM. 3 ppm and 130 ppm respectively, and the reaction mixture was heated at 56.5 ° C for 15 minutes and cooled. Desalination, stripping, centrifugation, drying, and sieving are then performed in the same manner as in Example 1, and the OVC resins obtained in the brain are similarly tested in the WPP assay.

Examples 7 and 8 (comparative)

Example 2 is repeated, except that the aqueous solution of OH-TEMPO is replaced by biphenol A (BPA), which is added as a 35% methanol solution, and is taken at 370 ppm relative to the initial VKM. Example 7) or by replacing OH-TEMPO with Irganox (R) 1141 (IGX 1141), which is in the form of a solution in 8% epoxidized soybean oil, which is 620 ppm relative to the added VKM. Example 8).

1-8. Example 1 and the results obtained are summarized in Table 1.

Table 1

Example number Megállítószer AP / At (mbar / min) Wippel denomination w / monomer M First no 0 0 40 35 Second OH-TEMPO 1.5 ppm 0.000078 25 nd Third OH-TEMPO 3 ppm 0.000157 15 nd 4th OH-TEMPO 6 ppm 0.000314 0 42 5th SG1 115 ppm 0.0035 0 nd 6th OH-TEMPO / DEHA 3 ppm / 130 ppm 0.000157 / 0.0131 0 40 7th BPA 370 ppm .0151 0 46 8th IGX 1141 620 ppm .0152 3 47

nd = not measured

OH-TEMPO acts as a stopper for polymerization in Figs. as the pressure drop rate decreases. The polymerization was stopped by 6 ppm OH-TEMPO. The resin has a good whiteness. In the case of SG1, the cessation of polymerization is already achieved at less than 115 ppm.

HU 226 900 Β1

Example 9

The procedure of Example 1 was followed except that 13.63 g of 40% active ingredient di (2-ethylhexyl) peroxydicarbonate emulsion (Luperox® 223 EN40) was 12.98 g of tert. butyl peroxy neodecanoate was replaced by a 40% drug emulsion (Luperox 10M75) and when the pressure drop reached 0.3 bar, 50 g of a 0.22% solution of 4-hydroxy-TEMPO was added over 2 minutes. , 12.5 ppm OH-TEMPO relative to the initial VKM, and the reaction mixture was heated at 56.5 ° C for 15 minutes and cooled.

Degassing, stripping, centrifugation, drying and sieving were then performed in an analogous manner to Example 1, and the resulting PVC was also tested by the WPP test as described in Example 1.

Example 10

The procedure of Example 9 was followed except that 100 g of 0.03% 4-hydroxy-TEMPO solution was used, using 3 ppm OH-TEMPO relative to the initial weight of the VKM. The results obtained in Examples 9 and 10 are summarized in Table 2.

Table 2

Example number Megállítószer ΔΡ / Δί (mbar / min) Wippel denomination w / monomer M 9th OH-TEMPO 12.5 ppm 0.00065 0 52.7 10th OH-TEMPO 3 ppm 0.000157 30 53.5

Example 11 14 kg of deionized water, 2.52 g of citric acid, 7.2 g of polyvinyl alcohol are added to a reactor with a triple l Impeller type 1 and a reactor with heating jacket at 250 rpm at room temperature. with a degree of hydrolysis of 78 mol%, 5.4 g of polyvinyl alcohol, with a degree of hydrolysis of 72 mol%, 3.06 g (39% active ingredient) of aqueous polyvinyl alcohol, having a degree of hydrolysis of 55 mol%. 30

The reactor was sealed and placed under partial vacuum (6.66 absolute kPa) and maintained for 30 minutes. The agitation is then increased to 330 rpm and 9 kg of VKM is added.

The heating is controlled so that a polymerization temperature of 70 ° C is reached within 45 minutes (at time ₀ ). At this temperature, 20 g of a solution containing 3.75 g of tert-butyl peroxypivalate (Luperox 11M75) and 16.25 g of isododecane are added.

After polymerization for a minute (i.e., at _t + 30 minutes at 40 points), 3.4 kg of water are continuously added to the reactor at a constant flow rate of 1.2 kg / h to improve the heat exchange by keeping the heating surface of the reactor constant, and to reduce the viscosity of the aqueous suspension after converting the VKM to 60% PVC. This conversion rate is calculated using a thermal balance at the edges of the reactor.

As soon as the pressure drop reaches 0.4 bar, 50 g of an aqueous solution of 0.09% OH-TEMPO is injected into the reaction mixture, 5 ppm relative to the initial weight of the VKM is taken from OH-TEMPO. The reaction mixture was maintained at 70 ° C for 15 minutes and then cooled.

Degassing, stripping, centrifugation, drying and sieving are then performed in the same manner as in Example 1. 55

The ΔΡ / At value and the WlPP were determined as described in Example 1.

The following results are obtained ΔΡ / At (mbar / min) = 0

Wippel = 63.4. 60

Examples 12 and 13 (Urgent cessation of polymerization)

Example 12

With a 1200 L three-way Impeller type stirrer, a "killer" nitrogen pressure vessel and a double jacketed reactor, 500 kg of deionized water, 90 g of citric acid, 132.5 g of poly (2 g) were added under stirring at room temperature (125 rpm). vinyl alcohol) with a degree of hydrolysis of 78 mol%, 132.5 g of polyvinyl alcohol having a degree of hydrolysis of 72 mol%, 112 g of aqueous polyvinyl alcohol (containing 39% active ingredient) solution having a degree of hydrolysis of 55 mol% and 166 g of di (2-ethylhexyl) peroxydicarbonate containing 75% active ingredient (Luperox® 223 M 75). The active oxygen content is 18 ppm relative to the weight of the VKM to be administered subsequently.

After the reactor is closed, the reactor is placed under partial vacuum (6.66 absolute kPa) and maintained for 30 minutes. The agitation is then increased to 250 rpm and 320 kg of VKM is added.

Cold water is circulated in the reactor cooler-jacket to control the heating to achieve a polymerization temperature of 56.5 ° C in 30 minutes. The moment when the polymerization medium reaches a temperature of 56.5 ° C, considered to be the beginning of the polymerization (time = t _0), the pressure measured at the moment (P _o) will be accepted by reference.

After polymerization in minutes (i.e., when the time t _o + 4O minutes) in the jacket to a cold water circulation is stopped. An increase in pressure and temperature is observed, which is characterized by DAT and ΔΡ / Δί.

The time instant t ₀ + 45 min to the reactor 170 g of an aqueous 5.88% w-OH TEMPO was added to the vessel under nitrogen pressure, that is dosed to the reactor relative to the weight of VKM 31 ppm OH-TEMPO are added.

The pressure and temperature changes are reported in Table 3.

HU 226 900 Β1

Example 13 (Comparative)

The procedure described in Example 12 was followed except that 1.5 liters of a 25% w / w solution of bisphenol A (BPA) in methanol was added at ₀ + 45 min, i.e., to the reactor.

1313 ppm BPA relative to the weight of the VKM was taken.

As in Example 12, changes in pressure and temperature are recorded and are shown in Table 3.

Table 3

example Number Killer AP / At (mbar / min) AP / At (mbar / min) mark crowd/ monomer adding the killer adding the killer before after before after 12th OH-TEMPO 31 ppm 60 0 0.2 0 13th BPA 1313 ppm 94 3 0.3 0.03

It can be seen that OH-TEMPO acts as a killer even at very low concentrations. 20

Claims (20)

CLAIMS 1. A process for the polymerization of vinyl chloride, alone or in admixture with less than 50% by weight of other vinyl monomers, in an aqueous suspension, characterized in that the polymerization initiator system comprises at least one of dialkyl peroxydicarbonates, peroxy tertiary alkanoates and a compound selected from the group consisting of diacyl peroxides and at least one polymerization agent selected from the group consisting of nitroxide-type stable radicals between 60-90% monomer conversion. The process according to claim 1, wherein the polymerization stopper is selected from the group consisting of nitroxides of formula I wherein Y ¹ -Y ⁶ , which may be the same or different, are hydrogen, C 1-10 straight or branched alkyl, C 3-20 cycloalkyl, halogen, cyano, phenyl, C 1-4 hydroxyalkyl, dialkoxy. -phosphonyl, diphenoxyphosphonyl, alkoxycarbonyl, alkoxycarbonylalkyl; or two or more groups of Y ¹ -Y ⁶ , taken together with the carbon atom to which they are attached, may form ring structures which may contain one or more of the following rings: H ₂ N-CH ₃ C (O) NH-, (CH ₃₎ ) ₂ NR ¹ C (O) O-, wherein R ¹ is a C 1-20 hydrocarbon group; or they may contain one or more heteroatoms, either ring or non-ring, such as oxygen or nitrogen. The process according to claim 2, wherein the nitroxides are used in pure form or in the form of a preparation. The process according to claim 2, wherein the polymerization stop agent is 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (4-hydroxy-TEMPO). The process according to claim 3 or 4, wherein the 4-hydroxy TEMPO is used in a formulation containing 0.01 to 90% by weight of 4-hydroxy TEMPO. The process according to claim 2, wherein the polymerization stop agent is N-tert-butyl-1-diethyl-1-phosphono-2,2-dimethyl-1-propyl-nitroxide (SG1). 7. A process according to any one of claims 1 to 3, wherein the nitroxide is used in combination with another polymerization stop agent, such as a dialkylhydroxylamine. The process of claim 7, wherein the dialkylhydroxylamine is diethylhydroxylamine. The process according to claim 1, wherein each alkyl group of the dialkyl peroxydicarbonate contains from 2 to 16 carbon atoms, preferably from 6 to 16 carbon atoms. The process according to claim 9, wherein the dialkyl peroxydicarbonate is di (2-ethylhexyl) peroxydicarbonate. The process of claim 1, wherein the polymerization initiator system comprises a dialkyl peroxydicarbonate and a very fast peroxy tertiary alkanoate. Process according to claim 11, characterized in that the very fast peroxy tertiary alkanoate is 1,1-dimethyl-3-hydroxybutyl peroxy neodecanoate. 13. The process according to claim 1, wherein the polymerization initiator system comprises a dialkyl peroxydicarbonate and a fast peroxy tertiary alkanoate. 14. The process of claim 1, wherein the polymerization initiator system is a mixture of a dialkyl peroxydicarbonate or a fast peroxy tertiary alkanoate and a diacyl peroxide. 15. The process of claim 14, wherein the fast peroxy tertiary alkanoate is tert-butyl peroxy neodecanoate and the diacyl peroxide is dilauroyl peroxide. The process of claim 1, wherein the polymerization initiator system is a mixture of two fast peroxy-tert-alkanoates or a very fast peroxy-tert-alkanoate and a fast peroxy-tert-alkanoate. HU 226 900 Β1 The process according to claim 16, wherein the very fast peroxy tertiary alkanoate is 1,1-dimethyl-3-hydroxybutyl peroxy neodecanoate. The process of claim 1, wherein the polymerization initiator system is a slow peroxy-tertiary alkanoate such as tert-butyl peroxy-pivalate. 19. Process according to any one of claims 1 to 3, characterized in that from 0.0001 to 0.1 parts by weight, preferably from 0.00015 to 0.01 parts by weight of the polymerization stopper are applied to 100 parts by weight of vinyl chloride alone or in combination with other vinyl derivative monomers. employed. 20. Vinyl chloride-based polymers and copolymers according to any one of claims 1-19. A process according to any one of claims 1 to 6.